Like Haddad, Khan has not advocated violence against his fellow UK citizens, but what might his audience have made of his tirade about the meaning of jihad when he explained that the "glory of the Muslim ummah" [global nation of believers] would only be revived when the "black ink . . . of the scholar" on a map of the world and the "red ink of the martyr . . . are put together". He said that to restore the map "to its original format [i.e. the Islamic empire] . . . only a few individuals . . . strive to . . . raise the word of Allah once again" but get "blamed" for "encouraging people . . . towards terrorism, towards bloodshed, towards evil action, to upheaval . . . Where is the evidence for this type of belief?"

According to Khan, when Islam finally dominates the map again, he "envisage[s] a beautiful time of victory" when Muslims can be "stern towards the disbelievers" and you will have "the right to show the power and the dominance of Islam. Even walking in the streets you shouldn't give them way."

While not advocating violence against UK citizens, it might be thought blindingly obvious that this angry and extreme world view championed by the likes of Khan and Haddad at least helps prepare the ground for violent extremism.

After all, terrorism is not just about violence for a specific purpose. Terrorists always draw on extreme ideology and the British jihadists who have joined IS have justified violence on the grounds of their beliefs. Non-violent extremist clerics like Haddad and Khan share some of the ideology of al-Qaeda and the extremist groups broadly sympathetic to them: namely, a triumphal belief in the superiority of Islam, a duty to work for the re-establishment of a caliphate by uniting Muslims under one interpretation of sharia, contempt for the West and its mores, and support for brutal punishments for "crimes" like adultery and apostasy, regarded in the West as matters of free conscience.

To take just one of those shared beliefs: hostility to our liberal, democratic, capitalist society, a view Salafist speakers often present forcefully to university Islamic societies. In 2008 Professor Martin Innes of Cardiff warned—presciently—that the threat to the UK from jihadist terrorism might increase. His research on behalf of the Association of Chief Police Officers showed that:

Increasing numbers of young Muslim people are becoming sufficiently disaffected with their lives in liberal-democratic-capitalist societies that they might be willing to support violent terrorism to articulate their disillusionment and disengagement.

Do those who discount a relationship between non-violent extremism and violent extremism believe that sentiments like Haddad's about democracy being "filthy" are likely to dispel, or exacerbate that "disillusionment and disengagement"?

Still, the Salafists rely heavily on a recent report from the former editor of Race and Class, now lecturing in terrorism studies at John Jay College, New York. Professor Arun Kundnani is also the author of The Muslims are Coming! Islamophobia, Extremism and the Domestic War on Terror. He says the idea that terrorism is caused by extremism—as defined by opposition to British values—"does not stand up to scholarly scrutiny."

Kundnani has set up a straw man. For he also says that the "factors which lead someone to commit acts of terrorism are complex and cannot be reduced to holding a set of values deemed to be radical." No one has said otherwise.

A sense of alienation fostering an identity crisis, absence of role models, foreign policy—all can interact with theo-political factors without pushing a person into violence. The Home Secretary, Theresa May, has said as much. But as she also says, the "damage" caused by non-violent extremism that "promotes intolerance, hatred and a sense of superiority over others . . . is reason enough to act. And there is, undoubtedly, a thread that binds" these beliefs "to the actions of those who want to impose their values on us through violence".